String(4)
console.log(String(false) ) //
console.log(String(null))
console.log(String(Symbol('s')))
// toString()
console.log(String({a:2}))
console.log(typeof String([]))
console.log(String([1,2]))
console.log([1,2].toString())  // toString
console.log(String(/reg/g))
var arr = [1,3];
arr.toString = function() {return this.join('/')}
console.log(String(arr))